Electronic equipment cases used in environments such as railway tunnels, mining operations, hydroelectric plants, sewer and pipe line installations, and highway tunnels and bridges, are subject to the accumulation of dust and debris within the electronic cabinet enclosure.
For example, in the case of a railway tunnel, a train creates a tremendous pressure as it enters the tunnel. Dust and other foreign matter, due to tunnel drilling, wear of metal wheels, and the like are forced into the electronic enclosure and dust and debris accumulates therein.
In the case of electronic enclosures used in railway tunnels, these enclosures typically house relay and switching gear critical to track operation. The switching gear may be adversely affected by debris and dust accumulating therein as well. This equipment also, in some instances, includes devices which generate heat and therefore there is a need to provide for heat exchange between the inside of the enclosure and the exterior environment.
It has been appreciated in the electronic arts that heat exchange is needed to cool electronic components within electronic modules. For example, U.S. Pat. No. 4,106,076 discloses a plurality of fans for circulating air within an electronic enclosure.
It has also been appreciated in the railroad arts that air cleaner systems which filter air for cooling electrical equipment are provided on diesel-electrical locomotives. See U.S. Pat. No. 3,771,293.
Up to this point, the art has failed to recognize the need for an electronic enclosure for use in an environment such as a railway tunnel in which an electronic cabinet assembly has a fan and a filter activated by a differential pressure switch for increasing the interior pressure to a level at or above the external pressure to prevent dust and/or debris from entering the interior environment and for providing heat exchange.
Another drawback of previous electronic enclosure is that these enclosures had multiple locks to keep the door shut. This is a regulatory requirement to have a lock for each door and failure to insure that each door is locked can result in citations and fines. Yet a further drawback of previous electronic enclosures is that they each were custom fabricated and not readily expandable.